Precious Frogs

I’m working a short term contract in the Fraser Valley collecting data for a capture-mark-recapture study on the Oregon Spotted Frog (Rana pretiosa)–Canada’s most endangered amphibian. But this job is far from work. Once I put on a pair of hip waders, stick my foot in that first step of thick oozing mud, and get a whiff of that familiar decomposing plant marshy smell, I feel like a kid again. That wide-eyed fascination and curiosity gets awakened inside of me. Wetlands are places where possibilities seem endless and open.

We spend our days checking small minnow traps (no need for bait!) that we set out in the wetland. Once we catch a frog, we scan it to see if we’ve already caught it before. If its a new frog, we insert a PIT tag (Passive Integrated Transponder). Basically, they are small little tags (about the shape and size of a grain of rice) that contain a series of numbers–kind of like a unique name. We can use a PIT tag reader to scan frogs and read out their unique number which can tell us when we last caught it. The goal of the study is to estimate the population size based on how many individuals we catch, and how many are ‘new’ and how many are frogs that we have already caught before (‘recaptures’).

Minnow trap that we use to catch the frogs. We don’t have to use bait, the frogs just go in and have trouble getting out again.

We use the PIT tag reader to scan each frog to read its unique number–or name.

The latin name for these frogs says everything about these beautiful creatures: Rana pretiosa means precious frog. It doesn’t take long to fall in love once you look into their golden-flecked eyes. Oregon Spotted Frogs are endangered in Canada (and are declining through-out their range in North America). There are only 3 remaining populations left in Canada, which we currently estimate to total 300 breeding females.

Gorgeous! The Oregon Spotted Frog’s colouring help it to blend in to its wetland surroundings.

These frogs seem to be dying the death of a thousand cuts. Habitat loss, degradation and fragmentation are huge contributors to their decline. Big open healthy wetlands are becoming increasingly rare as we drain more and more land for agriculture to feed our increasing human population size. Invasive species like Reed Canary Grass (Phalaris arundinacea) are also changing these wetland habitats. But it is the invasive Bullfrog (Lithobates catesbeianus), which are huge generalist predators, that make these wetland exceptionally inhospitable for Oregon Spotted Frogs. Bullfrogs like to eat our native endangered frogs as well as compete with them for resources. Like many other invasive species stories, we humans are to blame for their introduction to the Fraser Valley. Apparently we started farming bullfrogs in the hopes of developing a market for bullfrogs as a food source. When the business went belly up, all the frogs were released and have been spreading ever since.

American Bullfrog (Lithobates catesbeianus)

Reed Canary Grass (Phalaris arundinacea) is an invasive grass that that takes over areas that it invades and can dramatically alter the wetland habitat for the frogs

Everything about Oregon Spotted Frogs is elusive and mysterious. They are good at hiding, and are very aquatic, so we think they spend a lot of their time buried in muck. This makes them very hard to find, even when using technology like radio-telemetry. Their call is quite different from what would typically come to mind when you think of a frog call as they actually call underwater. The best way to describe it is like a soft tapping on a piece of wood. You can listen to a recording here.

I feel honoured to be able to see and touch these unique frogs. Like endangered Spotted Owls which have become the poster child for destruction and fragmentation for old growth forests on the West Coast, I feel like these spotted frogs are the ‘canary in the coal’ mine with respect to wetland health. Each frog echoes the story of destruction and fragmentation and carelessness, and the best we can do now is to listen.

For more information about Oregon Spotted Frogs, please see these links: